Quantifying Wet Antenna Attenuation in 38-GHz Commercial Microwave Links of Cellular Backhaul

Abstract

The quantification of wet antenna attenuat-ion (WAA) represents one of the major uncertainties in rainfall retrieval from commercial microwave links (CMLs). We propose identifying WAA distribution and upper limits based on rainfall climatology without the need for nearby rainfall observations. The quantified contributions of antenna wetting due to total loss are derived from 2 years of data collected from eight short (48–497 m) CMLs operating at frequencies of 37.3–39.2 GHz within the cellular backhaul. More specifically, the complementary cumulative distribution functions of measured attenuation are compared with theoretical ones calculated from rainfall data from local rain gauges. The results show that WAA reaches 1.5–2.0 dB and dominates over path attenuation during light rainfalls ( $R mm/h). WAA can, however, reach 2.8–5.3 dB during heavy rainfalls and maximal WAA observed during extreme rainfalls ( $R \approx 70$ –130 mm/h) is between 6–9 dB. The constant value of WAA used in some previous studies may, therefore, lead to a significant overestimation of peak rainfalls retrieved from CMLs.